The field of the invention oceanographic instrumentation, and more particularly to the invention relates to devices for passively maintaining near-neutral bouyancy in a known density versus depth environment.
All materials, and in particular hollow structures formed from a given material, exhibit a volume compressibility (a). This volume compressibility, when multiplied by nominal volume (V) and a pressure (P) yields the differential volume (.DELTA.V) that the structure will exhibit when exposed to the pressure P. In order to maintain neutral buoyancy of the structure in a liquid medium, it is essential that the structure have an indentical characteristic (.DELTA.V/P) to the medium in which is to be submerged. However, in practice, it is difficult to match the .DELTA.V/P characteristic of a structure to a real-world medium, such as the ocean. Generally, a compensation scheme must be employed in order to maintain essentially constant buoyancy for the structure over a predetermined range of depths.
In the oceans for example, there are water density versus depth profiles that vary significantly world-wide. In order to provide a structure, or device, that may be immersed in such a liquid medium, so that the structure maintains a desired buoyancy (either positive, neutral, or negative) regardless of depth of submersion, the specific water density versus depth profile must be exactly compensated for at the exact geographic location where the structure is to be submerged. There are prior art approaches to providing such compensation which require "active" mechanizations. While such approaches are effective in providing the desired compensation, the active nature of such mechanization generally requires an onboard power supply and, in some implementations, gas generating devices. The addition of such supplies and devices requires a corresponding expense, as well as provides reliability limitations on the structure.
It is an object of the present invention to provide a passive structure having a controlled bouyancy in a non-linear density versus depth medium environment.